The disclosures herein relate generally to collapse resistant umbilical structures and more particularly to gas lift umbilical and end termination assemblies.
Oil from oil bearing reservoirs is sometimes produced by the inherent reservoir pressure. In many cases, however, the reservoir lacks sufficient inherent pressure to force the oil from the reservoir upwardly to a wellhead structure where the oil is transported from the wellhead structure by flowlines. When the pressure of a production zone of a reservoir is not sufficient to force the oil products to the wellhead under the inherent pressure of the reservoir, a number of methods may be used to artificially produce pressure to force the oil products to the wellhead.
One common method is known as gas lift whereby gas is injected through a gas lift hose under controlled pressure into the annulus between the production tubing and the well casing. The gas mixes with and aerates the fluids in the production tubing thereby providing a lifting force for lifting the fluids to the surface. The gas that is injected is commonly referred to as an export gas. Methanol may also be injected to reduce the amount of wax accumulated in the production lines.
In deep water subsea oil field operations, umbilicals, hoses, risers and the like generally must be resistant to collapse due to hydrostatic pressure. The collapse pressure is the external hydrostatic pressure required to cause the umbilical structure to buckle. The hydrostatic pressure is proportional to the depth of the seawater such that the hydrostatic pressure increases with increasing seawater depths. For example, at a water depth of 340 meters, the hydrostatic pressure is approximately 500 psi.
Gas lift hoses are commonly used in subsea oil production operations. A typical gas lift hose includes a core, an inner sheath, a kevlar-aramid armor layer and an outer sheath. However, commercially/available gas lift hoses generally do not have sufficient compressive hoop strength to resist hydrostatic collapse. These types of hoses are typically constantly pressurized to prevent the hose from collapsing. In the event that pressure is lost, the hose will collapse due to the hydrostatic pressure. It is common for the collapse to result in permanent damage to the hose. A common alternative design for gas lift hose elements is to add a carcass internal to the hose. This carcass is typically some type of steel to resist the hydrostatic pressure. This requires different production processes and equipment than is normally used.
Accordingly, a need has arisen for an apparatus that is configured to overcome the shortcomings of prior art and, in particular, a core of a gas lift umbilical cable that utilizes collapsible gas lift hoses within a non-collapsible flexible pipe.